#### 12th Standard Chemistry English Medium Ionic Equillibrium Reduced Syllabus Important Questions 2021

12th Standard

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Chemistry

Time : 01:00:00 Hrs
Total Marks : 100

Multiple Choice Questions

15 x 1 = 15
1. Concentration of the Ag+ ions in a saturated solution of Ag2C2O4 is 2.24 ×10-4mol L-1 solubility product of Ag2C2O4 is

(a)

2.42 ×10-8mol3L-3

(b)

2.66 ×10-12mol3L-3

(c)

4.5 ×10-11mol3L-3

(d)

5.619 ×10-12mol3L-3

2. pH of a saturated solution of Ca(OH)2 is 9. The Solubility product ( Ksp) of Ca(OH)2

(a)

0.5 ×10-15

(b)

0.25 ×10-10

(c)

0.125 ×10-15

(d)

0.5 ×10-10

3. Conjugate base for bronsted acids H2O and HF are

(a)

OH- and H2FH+ , respectively

(b)

H3O+ and F, respectively

(c)

OH- and F-, respectively

(d)

H3O+ and H2F+, respectively

4. Which will make basic buffer?

(a)

50 mL of 0.1M NaOH+25mL of 0.1M CH3 COOH

(b)

100 mL of 0.1M CH3COOH+100 mL of 0.1M NH4OH

(c)

100 mL of 0.1M HCl+200 mL of 0.1M NH4OH

(d)

100 mL of 0.1M HCl+100 mL of 0.1M NaOH

5. MY and NY3, are insoluble salts and have the same Ksp values of 6.2 ×10-13 at room temperature. Which statement would be true with regard to MY and NY3?

(a)

The salts MY and NY3 are more soluble in 0.5M KY than in pure water

(b)

The addition of the salt of KY to the suspension of MY and NY3 will have no effect on their solubility’s

(c)

The molar solubilities of MY and NY3 in water are identical

(d)

The molar solubility of MY in water is less than that of NY3

6. The hydrogen ion concentration of a buffer solution consisting of a weak acid and its salts is given by

(a)

$[{ H }^{ + }]=\frac { { K }_{ a }[acid] }{ [salt] }$

(b)

$[{ H }^{ + }]={ K }_{ a }[salt]$

(c)

$[{ H }^{ + }]={ K }_{ a }[acid]$

(d)

$[{ H }^{ + }]=\frac { { K }_{ a }[salt] }{ [acid] }$

7. With regard to the strength of acids and bases, Find the incorrect statement among the following.

(a)

Strong acid is one that completely dissociates in water

(b)

Ka is the dissociation constant

(c)

CH3COOH is a weak acid

(d)

Smaller the Ka value, greater is the acid strength

8. Krepresents

(a)

ionic product constant of water

(b)

Solubility product of water

(c)

Equilibrium constant of water

(d)

Buffer index

9. The buffer present in human blood is

(a)

CH3COOH + CH3COONa

(b)

NH4OH + NH4CI

(c)

H2CO3 + H${ CO }_{ 3 }^{ - }$

(d)

CH3COOH + CH3COONa and NH4OH + NH4CI

10. The condition for a compound to be precipitated is

(a)

Ionic product = solubility product

(b)

Ionic product < solubility product

(c)

Ionic product > solubility product

(d)

Ionic product ≤ solubility product

11.  Which among the following is incorrect regarding acids?

(a)

It produces H+ ions in aqueous solution

(b)

It can donate a proton to another substance

(c)

It can accept a proton from another substance

(d)

It accepts a pair of electrons

12. Henderson equation for a weak acid and its salt is

(a)

pH= pKb+log (Salt) / (Acid)

(b)

pH = pKa + log (Salt) / (Acid)

(c)

pH = pKa +log (Salt) / (Base)

(d)

pH = pKa + log (Acid) / (Salt)

13. An acid is a substance that dissociates to give hydrogen ions in water.
The above concept of acids was proposed by ______________

(a)

Lewis

(b)

Arrhenius

(c)

Bronsted

(d)

Lowry

14. If ionic product < solubility product then the solution is ________

(a)

saturated

(b)

super saturated

(c)

unsaturated

(d)

none of the above

15. The solution whose pH is maintained constant even upon the addition of small amounts of acid or base is called ________

(a)

acidic solution

(b)

basic solution

(c)

buffer solution

(d)

true solution

1. 2 Marks

10 x 2 = 20
16. What are lewis acids and bases? Give two example for each.

17. Discuss the Lowery – Bronsted concept of acids and bases.

18. Indentify the conjugate acid base pair for the following reaction in aqueous solution
i) HS- (aq) + HF $\rightleftharpoons$ F-(aq) + H2S(aq)
ii) HPO2-+ SO32- $\rightleftharpoons$ PO43-+HSO3-
iii) NH4+ CO32-  $\rightleftharpoons$ NH3+HCO3-

19. When aqueous ammonia is added to CuSO4 solution, the solution turns deep blue due to the formation of tetramminecopper (II) complex,${ [Cu({ H }_{ 2 }O)] }_{ (aq) }^{ 2+ }\rightleftharpoons 4{ NH }_{ 3 }(aq)\rightleftharpoons { [Cu{ ({ NH }_{ 3 }) }_{ 4 }] }_{ (aq) }^{ 2+ }$ among H2O and NH3 Which is stronger Lewis base.

20. Define solubility product

21. Calculate pH of 10-7M HCl

22. Give the Limitations of Arrhenius concept theory of acids and bases

23. What are the two types of buffer? Give an example for each.

24. How is common ion effect related to the solubility of the electrolyte?

25. What are the limitations of Ostwald's dilution law?

1. 3 Marks

10 x 3 = 30
26. Explain common ion effect with an example

27. Calculate the pH of 1.5$\times$10-3Msolution of Ba(OH)2

28. The Ka value for HCN is 10-9 . What is the pH of 0.4M HCN solution?

29. Derive an expression for the hydrolysis constant and degree of hydrolysis of salt of strong acid and weak base

30.  Fine the pH of a buffer solution containing 0.20 mole per litre sodium acetate and 0.18 mole per litre acetic acid. Ka for acetic acid is $1.8\times10^{-5}$.

31. Based on Arrhenius concept, defme acid and bases and give an example for each.

32. What do you mean by auto ionisation of water?

33. How will you calculate solubility product from molar solubility?

34. What is Henderson equation?

35. What do you mean by buffer action?

1. 5 Marks

7 x 5 = 35
36. A saturated solution, prepared by dissolving CaF2(s) in water, has $[Ca^{2+}]=3.3\times10^{-4}M$ What is theKsp of CaF2?

37. Ksp of Al(OH)3 is 1$\times$10-15M. At what pH does 1.0×10-3M Al3+ precipitate on the addition of buffer of NH4Cl and NH4OH solution?

38. Establish a relationship between the solubility product and molar solubility for the following
a) BaSO b)Ag2(CrO4)

39. Calculate the pH of a buffer mixture which contains 7.5 gms if acetic acid and 10.25 gms of sodium acetate in 1 litre of the solution. Ka for acetic acid is 1.8 x 10-5.

40. A buffer solution containing 0.1 mole of ammonium hydroxide and 0.15 mole of ammonium chloride per litre of the solution. Calculate the pH of the buffer solution. Kb for ammonium hydroxide is 1.8 x 10-5.

41. Explain buffer action in an acidic buffer.

42. Derive Henderson - Hasselbalch equation